Is it ensure, insure, or assure?
1562, from Middle French Huguenot, according to French sources originally political, not religious. The name was applied in 1520s to Genevan partisans opposed to the Duke of Savoy (who joined Geneva to the Swiss Confederation), and it is probably an alteration of Swiss German Eidgenoss "confederate," from Middle High German eitgenoze, from eit "oath" + genoze "comrade" (related to Old English geneat "comrade, companion"). The form of the French word probably altered by association with Hugues Besançon, leader of the Genevan partisans. In France, applied generally to French Protestants because Geneva was a Calvinist center.
French Protestants of the sixteenth and seventeenth centuries, who were frequently persecuted by the government and by the Roman Catholic Church. For a time, the Edict of Nantes allowed them to practice their religion in certain cities. When the edict was revoked by King Louis xiv in the late seventeenth century, many Huguenots left France. Some emigrated to America.